This is a proposal for a multi-disciplinary research program project involving the departments of Community Health, Neurology, Psychiatry and Pharmacy. It consists of a core cross-sectional and longitudinal population survey and four research projects based upon it. A population sample consisting of some 2,000 elderly community residents will provide the necessary subjects and data required for the initiation and execution of the four research projects. The overall effort will be accomplished over a period of five years. The four projects are: a) Core Health Study - investigating the relative effectiveness of the receipt of health care in maintaining the health and social functioning of a representative sample of elderly persons residing in a defined urban community. b) Antecedents of Depression and Dementia in the Community Aged - investigating the nature and prevalence of depression and its risk factors and co-existing dementia in a case control study. c) Assessment of Medication in the Elderly and Impact of Pharmacist Intervention-investigating the prevalence of drug use and its problems in the aged and the subsequent impact of pharmacist intervention. d) Sleep Disorders in the Elderly - investigating, in a series of studies on sleepwake disorders and hypnotic drug use, the prevalence of the problems. Both retrospective and prospective case-control studies and an intervention study are included.